1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Phase issues... am I understanding this right?

Discussion in 'Effects [BG]' started by JACink, Feb 2, 2018.


  1. JACink

    JACink

    Mar 9, 2011
    Spain
    I am still new to the world of effects pedals, until recently I had been running only a Zoom B3 into a DAW, which means I had plenty of effects available and didn't have to worry about phasing issues, or blending issues etc.

    I am putting together a pedal board at the moment and I mentioned the other day in another thread about splitting and blending dry signal with wet.

    It was mentioned in that thread, along with many others that I have read, about possible phase issues when blending back dry signal.

    Here is a quote from dannybuoy who gave me some good info to think about. I have extracted just the part about phase issues:

    So, I understand the whole phase thing, and how certain pedals can invert the phase, but I wan't to confirm that I am actually understanding a few things correctly.

    1. As said, if you have any odd number of pedals that inverts the phase, then your dry signal will need to have the phase reversed in order to not experience cancellation. However, the pedal only inverts the phase when it is on (if it is True Bypass), which means that if you switch the pedal on and off during a song, you would have an issue each time the pedal is on (or off, depending on the chain). In this case, a phase reverse switch would just reverse the issue. Do people use some kind of phase reversal pedal that they hit at the same time?

    2. In order to reverse the phase, the signal would need to be balanced, reversed, and then unbalanced again. Correct? Is there a pedal that does this?

    3. To check if a pedal reverses phase, I could split my signal and send a dry and wet on different channels of my DAW and compare waves. Is it this simple or am I missing something?

    4. If I work out what pedals invert phase and would be used on their own, could I place them in an effects loop of there own, along with another "transparent" circuit that just inverts phase? I am thinking alond the lines of RDL unbalanced to balanced transformer connected to an RDL balanced to unblanced transformer with the phases inverted between them. This is something that I want to avoid, but would it be a solution if needed?

    5. Rather than the solution in point 4, could I just place the same "transformer" circuit at the end of the line (in a True Bypass loop) and try to switch it on as soon as possible when needed?


    Sorry for all the questions, I much appreciate any input. You don't need to explain it as though I were 5, but for under 7's would be good :D
     
  2. XLunacy

    XLunacy

    Nov 28, 2013
    France
    Hey :)

    1. If you have a single pedal that reverses phase, you could always put it into its own loop along with a phase inverter ; that way you would not have to switch 2 pedals at the same time

    2. Not sure why you'd need to balance and then unbalance the signal ? I don't know of a pedal that only serves as a phase inverter, but many pedals have a phase inverting system that you can toggle (I suggested a blender pedal in the other thread that does that)
    I think you could also use a cable that has inverted connectors but I'm not sure about that, might need some digging to be sure

    3. I'd say yes, it's that simple. It might become harder if the pedal distorts the signal a lot, but you should be fine by lowering the amount of "wetness" of said pedal

    4. Yes, but your pedalboard will quickly become way more complicated than it should. Hopefully you won't have to !

    5. Will work BUT you'd have to remember in which case you have to switch it or not as you're not always in the best conditions to judge by ear, and the attention / concentration you're putting into this might ruin your experience when playing live. IMO you should not think more than you have to, especially live, because there's already so much to care about :)
     
    JACink likes this.
  3. JACink

    JACink

    Mar 9, 2011
    Spain
    Thanks for the reply @XLunacy!

    Regarding the loop pedal that you suggested in the other thread, this has a phase inversion switch, but that would only reverse the issue wouldn't it? In other words, I would still have isues when turning pedals on or off, just that the issue would be the opposite of the issue without that switch?

    Regarding the transforming to balanced then back, the only way I know of inverting the phase is on a balanced (3 core) connection, on an unbalanced you just have hot and earth, or am I missing something?
     
  4. XLunacy

    XLunacy

    Nov 28, 2013
    France
    I do hope that the pedal's designer has made it so that the phase inversion is only applied to the FX loop when it is engaged ! If so then you're good with that pedal. Should be documented in the manual :)
    Can't help with phase inversion circuits because I don't know how they're implemented or anything else about them, just what they do !
     
    JACink likes this.
  5. JACink

    JACink

    Mar 9, 2011
    Spain
    Bump in search of knowledge ;)
     
  6. boomertech

    boomertech Frank Appleton Supporting Member Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    Phase inversion (or polarity inversion) is usually heard as a low frequency suck. Most times a phase flip (or polarity flip) on either of the parallel blended signals will cure this issue. There are a few pedals that can have a large enough phase shift between 0 and 180 degrees that they can not be parallel blended with a simple phase flip device.

    The easiest way to overcome this phase flip issue would be to use only pedals where the outputs are in-phase with their inputs for pedals that you will be switching on-off. If you use inverting pedals then always keep in mind the odd numbers of inverting pedals will flip phase and even numbers will put the signal back into phase with the dry signal.

    There are many was to flip phase with electronics. The two easiest and cheapest ways are to use an inverting opamp circuit or a simple transistor phase-splitter. The opamp circuit will be a dollar or two more than the transistor circuit but it will have the benefit of rejecting power supply noise for a quieter circuit.

    -Frank
     
    JACink likes this.
  7. JACink

    JACink

    Mar 9, 2011
    Spain
    Thank you Frank :thumbsup:
     

Share This Page